As more people consider organic products to be healthier, the practice of organic agriculture is expanding worldwide, accompanied by their high economic potential and environmentally sound practices. In organic farming, where the use of chemicals is prohibited, composts and fowl manures serve as fertilizers, mainly as a nitrogen (N) source. Supplementary N side dressing is needed in organic cropping systems when the available N from soils and composted manures applied annually is inadequate to meet crop requirements. Such conditions prevail in soils that have recently been converted to organic farming or in high-N demanding crops. In Israel, for example, the intensive growth of most organic crops in greenhouses is based on exploitation of composts prior to planting, and application of organic N during the growing season via the irrigation system (fertigation), particularly in drip irrigation. This practice allows uniform spreading of the N and reduces labor expenses connected with fertilizing operations [Yekutieli et al.: The field 76 (1996) 85-88]. Manure extracts have also been suggested as organic treatments against plant diseases [see, e.g., Welke S.: Effectiveness of compost teas extracts as disease suppressants in fresh market crops. Information bulletin 9 (2001) 16-20]. A major organic N source is guano, a natural deposit of the excrements and remains of birds living along ocean coasts and feeding on fish, which contains 15-20% N of its dry weight. Beside being expensive (approximately US$ 800/ton), it can be a source for diseases and pollution. On the other hand, recycling local chicken manure for organic agriculture would reduce occurrences of odor nuisance, disease and environmental pollution. Layer and Broiler manures contain approximately 4% N; however, their low price (˜US$ 25/ton) and availability can significantly reduce fertilization costs and environmental risks [Hadas A. The field 77 (1997) 18-20]. The most common practice for liquid N production in organic agriculture is to brew the manures in water at a ratio of 1/10 of dry manure/water for at least 10 d, as required by organic practice, forming an ammonia rich solution. The accepted guano extract contains, apart from the desired N, additional constituents, some of which can cause negative effects to the crop and to the environment (i.e. traces of hormones, excess nutrients, and pathogens). The extraction efficiency, in manure extracting, is usually about 10%. For most purposes, however, the preferred efficiency would be higher, and, furthermore, preferred form of N would be nitrate (ammonia is the dominant N source in the extracts). It is therefore an object of the invention to provide a process for the extraction of nitrogen from organic wastes, preferably manures, with improved N extraction efficiency.
It is another object of this invention to provide a method for the extraction of nitrogen from organic wastes and manures, comprising separating ammonia from the extract, and converting said ammonia to nitrate in a microbial process.
It is still another object of this invention to provide a method for the extraction of nitrogen from organic wastes and manures, comprising improving the fertilizer quality of the extract, and minimizing potential environmental pollution.
It is a further object of the invention to provide a nitrogen rich extract from fowl manure for use in organic agriculture.
Other objects and advantages of present invention will appear as description proceeds.